Fuel composition based on paraffinic hydrocarbons

ABSTRACT

The subject matter of the present invention is a fuel composition which comprises —at least 85% by weight of one or more fractions of hydrocarbons having a distillation range within the range extending from 100 to 400° C. and having a paraffin content greater than or equal to 90% by weight; —at least a first additive consisting of a particular quaternary ammonium salt; and —at least a second additive consisting of a phenolic antioxidant. The subject matter of the invention is also the use of a composition of additives comprising said first and second additives, for improving at least one property of a paraffin-rich fuel composition.

The present invention relates to the use of a fuel composition based on one or more paraffin-rich fractions which comprises at least one first additive consisting of a quaternary ammonium salt in association with at least one second additive selected from phenolic antioxidants.

The present invention also relates to the use of a composition of additives comprising the association of said first and second additives, in order to improve the properties of a fuel composition comprising a high paraffin content.

The present invention also relates to the use of such a fuel composition for supplying a diesel engine.

PRIOR ART

The use of hydrocarbon fractions that are particularly rich in paraffins in formulating fuels and in particular fuels for engines with compression ignition (or diesel engines) is becoming more and more usual. Hydrotreated vegetable oils, known to a person skilled in the art by the term HVO, constitute a classic example of fractions that are very rich in paraffins, which can be incorporated in greater or lesser proportions in fuels intended for road vehicles (in particular cars and goods vehicles such as for example lorries, refuse trucks, buses and coaches) and in non-road vehicles (in particular machinery intended for building sites and/or civil engineering works such as bulldozers, off-road lorries; handling machinery; tractors and agricultural machines; boats; locomotives, etc.).

The tendency is to more and more increase the proportions of such hydrocarbon fractions compared with conventional fractions resulting from the distillation of oil, or even to seek to formulate fuel compositions exclusively from such fractions. In particular, for environmental reasons and/or reasons of availability of resources, the regulations in many countries encourage introducing increasing quantities of products of renewable origin, such as fractions of the HVO type. This is because HVOs do not have the harmful effects that may be caused by biodiesels of the ester type, such as an increase in NOx emissions, the formation of deposits, etc.

However, formulating a fuel composition comprising a very high paraffin content poses a certain number of difficulties.

In particular, these fuels have proved to have poor resistance to corrosion, very appreciably inferior to that of fuels of petroleum origin. The use thereof may lead to phenomenon of rust and corrosion of the materials with which these fuels are in contact, in particular at the stage of the logistics of distribution of these fuels, transport, storage, systems for supplying vehicles with fuel).

In addition, such fuels lead to a phenomenon of extraction of metals: they have a tendency to extract certain metals, in particular copper and zinc, from the materials with which they are put in contact (for example the materials of the transport and storage devices, systems for supplying vehicles with fuel, etc.).

They also have low conductivity, related to the paraffinic nature thereof. However, fuels with low conductivity pose a problem during fuel transfers (in particular at the time of filling the vehicle tank): by friction or potential difference, electrical discharges may take place if the fuel is not sufficiently conductive, which causes risks of fire.

Finally, these fuels pose particular problems of stability in storage and in use: in the case of prolonged storage or in the case of use under conditions of high pressures or temperatures, the product has a tendency to oxidise and to degrade. This phenomenon is catalysed by any metals present in the fuel composition. This instability of the fuel may lead to phenomena of soiling of the filters and fuel injection systems in the vehicles.

The patent application WO 2015/193463 (Shell) describes the use of a combination of detergents (i), lubrication improvers and conductivity improvers (ii), in a diesel fuel composition containing a substantial paraffin content (in particular n-paraffins resulting from a Fischer-Tropsch synthesis) as well as an antioxidant.

The antioxidant is in particular selected from phenolic compounds and amines. The synergic combination of the antioxidant with compounds (i) and (ii) in a diesel fuel with a high n-paraffin content is described as significantly increasing the stability of the fuel with regard to oxidation.

Object of the Invention

The applicant has now discovered that using a particular combination of two additives, as defined below, made it possible to effectively remedy the aforementioned problems, and to allow the formulation of paraffin-rich fuel compositions having improved properties.

Thus the object of the present invention is a fuel composition comprising:

at least 85% by weight one or more hydrocarbon fractions having a distillation range within the range from 100 to 400° C. and having a paraffin content greater than or equal to 90% by weight;

at least one first additive consisting of a quaternary ammonium salt, obtained by reaction with a quaternarization agent of a nitrogenous compound comprising a tertiary amine function, this compound being the product of reacting a polyisobutenyl succinic anhydride and a compound comprising at least one tertiary amine group and at least one group selected from primary amines, secondary amines and alcohols; and

at least one second additive consisting of an antioxidant selected from the compounds comprising a phenol group.

Such a fuel composition has excellent anticorrosion performance, and makes it possible to avoid corrosion phenomena in the presence of both fresh water and salt water.

It also very significantly improves the stability of the fuel in the presence of metals, and has a very good conductivity.

This composition has an excellent stability level and in particular good stability in storage, good thermal stability, and more generally good resistance to oxidation.

Finally, this composition has also proved to have good detergent performance, and use thereof makes it possible not only to maintain the cleanliness of the engine, in particular by limiting or preventing the formation of deposits (“keep-clean” effect) but also reducing the deposits already present in the internal parts of the engine (“clean-up” effect).

It should be noted that these properties are improved without any degradation of the other intrinsic properties of the compositions based on paraffin-rich fractions, such as in particular their low level of foaming and de-emulsifying, their density, their ketane index, their good resistance to cold in the case of isoparaffin-rich fractions (limit temperature of filterability and flow point).

Its excellent properties make this fuel able to be used in modern motor vehicles, in particular vehicles comprising a diesel engine, including the most improved engines such as diesel engines with very high pressure direct injection.

Other objects, features, aspects and advantages of the invention will appear even more clearly from a reading of the following description and examples.

In the following, and unless otherwise indicated, the bounds of a range of values lie in this range, in particular in the expressions “included between” and “ranging from . . . to . . . ”.

Moreover, the expressions “at least one” and “at least” used in the present description are respectively equal to the expressions “one or more” and “greater than or equal to”.

Finally, as is known per se, a CN compound or group means a compound or a group containing N carbon atoms in its chemical structure.

DETAILED DESCRIPTION

The Paraffinic Hydrocarbon Fraction

The composition according to the invention comprises one or more hydrocarbon fractions having a distillation range lying in the range from 100 to 400° C. and having a paraffin content greater than or equal to 90% by weight, hereinafter referred to as “paraffinic hydrocarbon fraction”.

The distillation range of said paraffinic hydrocarbon fraction is determined in accordance with NF EN ISO 3405. Preferably, it lies in the range from 130 to 350° C., and more preferentially from 150 to 320° C.

The paraffin content of this fraction is greater than or equal to 90% by weight, preferably greater than or equal to 95% by weight, more preferentially still greater than or equal to 99% by weight, even better still greater than or equal to 99.5% by weight, and even better greater than or equal to 99.9% by weight, with respect to the total weight of said fraction.

“Paraffins” means, as is known per se, branched alkanes (also referred to as isoparaffins or isoalkanes) and non-branched alkanes (also referred to as n-paraffins or n-alkanes).

The paraffins present in the paraffinic hydrocarbon fraction or fractions according to the invention advantageously comprise from 10 to 20 carbon atoms. They preferably consist of at least 60% by weight, more preferentially at least 80% by weight and even better at least 90% by weight paraffins comprising from 12 to 18 carbon atoms, preferably from 14 to 18 carbon atoms, and even more preferentially from 15 to 18 carbon atoms.

According to a preferred embodiment, the paraffinic hydrocarbon fraction or fractions used in the composition according to the invention contain at least 50% by weight, preferably at least 70% by weight isoparaffins, with respect to the total weight thereof. According to a particularly preferred embodiment, they contain at least 90% by weight isoparaffins.

The paraffinic hydrocarbon fraction or fractions have an aromatic compound content preferably less than or equal to 10,000 ppm by weight, more preferentially less than or equal to 1500 ppm by weight, even more preferentially less than or equal to 1000 ppm by weight.

The naphthenic-compound content is preferably less than or equal to 20,000 ppm by weight, more preferentially less than or equal to 10,000 ppm by weight, and even better less than or equal to 1500 ppm by weight.

The sulfur content is advantageously less than or equal to 10 ppm by weight, and even better less than or equal to 5 ppm by weight. Particularly preferably, this fraction is completely free from sulfur.

According to a particularly preferred embodiment, the paraffinic hydrocarbon fraction or fractions are hydrotreated vegetable oils, also known by the term HVO. These are oils of vegetable origin that have undergone successive treatments including a hydrotreatment and then optional isomerisation.

Examples of suitable plant raw materials comprise colza oil, rapeseed oil, sunflower oil, soya oil, hemp oil, olive oil, linseed oil, mustard seed oil, palm oil, castor oil and coconut oil.

The patent applications WO2016/185046 and WO2016/185047 describe hydrotreated plant oils and preparation thereof, which constitute examples of isoparaffinic hydrocarbon fractions that are particularly suitable for the compositions that are the object of the present invention.

The composition according to the invention comprises at least 85% by weight one or more paraffinic hydrocarbon fractions as described above. Preferably, it contains at least 90% by weight one or more paraffinic hydrocarbon fractions, more preferentially at least 93% by weight.

According to one embodiment, the composition according to the invention contains at least 95% by weight, preferably at least 99% by weight and even better at least 99.5% by weight one or more paraffinic hydrocarbon fractions as described above.

The First Additive (Quaternary Ammonium Salt):

The composition according to the invention comprises a first additive consisting of a quaternary ammonium salt, obtained by reacting with a quaternarization agent a nitrogenous compound comprising a tertiary amine function, this nitrogenous compound being the product of the reaction of a polyisobutenyl succinic anhydride and a compound comprising at least one tertiary amine group and at least one group selected from primary amines, secondary amines and alcohols.

Said nitrogenous compound is the product of the reaction of a polyisobutenyl succinic anhydride (PIBSA) and a compound comprising both an oxygen atom and a nitrogen atom capable of condensing with said polyisobutenyl succinic anhydride and a tertiary amine group.

The polyisobutene (PIB) group preferably has a number mean molecular mass (Mn) of between 170 and 2800, for example between 250 and 1500, more preferentially between 500 and 1500 and even more preferentially between 500 and 1100. A range of values of Mn of between 700 and 1300 is particularly preferred, for example from 700 to 1000.

So-called highly reactive polyisobutenes (PIBs) are particularly preferred. Highly reactive polyisobutenes (PIBs) means polyisobutenes (PIBs) wherein at least 50% molar, preferably at least 70% molar or more, of the double terminal olefin bonds are of the vinylidene type as described in the document EP0565285. In particular, the preferred PIBs are those having more than 80% molar and up to 100% vinylidene terminal groups as described in the document EP1344785.

The preparation of polyisobutenyl succinic anhydrides is known per se, and widely described in the literature. Mention can be made for example of the methods comprising the reaction between polyisobutenes (PIBs) and maleic anhydride described in the documents U.S. Pat. Nos. 3,361,673 and 3,018,250, or the method comprising the reaction of a halogenated, in particular chlorinated, polyisobutene (PIB) with maleic anhydride (U.S. Pat. No. 3,172,892).

According to a variant, polyisobutenyl succinic anhydride can be prepared by mixing a polyolefin with maleic anhydride and then passing chlorine through the mixture (GB949981).

Said compound comprising at least tertiary amine group and at least one group selected from primary amines, secondary amines and alcohols may, for example be selected from the group consisting of: N,N-dimethylaminopropylamine, N,N-diethylaminopropylamine and N,N-dimethylaminoethylamine. Said compound may furthermore be selected from the heterocyclic compounds substituted by alkylamines such as 1-(3-aminopropyl)imidazole and 4-(3-aminopropyl)morpholine, 1-(2-aminoethyl)piperidine, 3,3-diamino-N-methyldipropylamine, and 3′3-bisamino(N,N-dimethylpropylamine).

The compound comprising at least one tertiary amine group and at least one group selected from primary amines, secondary amines and alcohols may also be selected from alkanolamines, including, but without thereby limiting, triethanolamine, trimethanolamine, N,N-dimethylaminopropanol, N,N-dimethylaminoethanol, N,N-diethylaminopropanol, N,N-diethylaminoethanol, N,N-diethylaminobutanol, N,N,N-tris(hydroxyethyl)amine, N,N,N-tris(hydroxymethyl)amine, N,N,N tris(aminoethyl)amine, N,N-dibutylaminopropylamine and N,N,N′-trimethyl-N′-hydroxyethyl-bisaminoethylether, la N,N-bis(3-dimethylamino-propyl)-N-isopropanolamine, la N-(3-dimethylamino-propyl)-N,N-diisopropanolamine, N′-(3-(dimethylamino)propyl)-N,N-dimethyl-1,3-propanediamine; 2-(2-dimethylaminoethoxy)ethanol and N,N,N′-trimethylaminoethylethanolamine.

According to a preferred embodiment, said compound comprising at least one tertiary amine and at least one group selected from primary amines, secondary amines and alcohol is selected from the amines of the following formula (I) or (II):

wherein: R6 and R7 are identical or different and represent, independently of each other, an alkyl group having from 1 to 22 carbon atoms; X is an alkylene group having from 1 to 20 carbon atoms; m is an integer number between 1 and 5; n is an integer number between 0 and 20; and R8 is a hydrogen atom or a C1 to C22 alkyl group.

When the nitrogenous compound comprises an amine of formula (I), R8 is advantageously a hydrogen atom or a C1 to C16 alkyl group, preferably a C1 to C10 alkyl group, even more preferentially a C1 to C6 alkyl group. R8 may for example be selected from the group consisting of hydrogen, methyl, ethyl, propyl, butyl and isomers thereof. Preferably R8 is a hydrogen atom.

When the nitrogenous compound comprises an amine of formula (II), m is preferably equal to 2 to 3, more preferentially equal to 2; n is preferably an integer between 0 and 15, more preferentially between 0 and 10, even more preferentially between 0 and 5. Advantageously n equals 0.

According to a preferential embodiment, said nitrogenous compound is the product of the reaction of a polyisobutenyl succinic anhydride and a diamine of formula (I).

In this embodiment:

-   -   R6 and R7 may represent, independently of each other, a C1 to         C16 alkyl group, preferably a C1 to C10 alkyl group;

R6 and R7 may represent, independently of each other, a methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl or octyl group or isomers thereof. Advantageously R6 and R7 represent, independently of each other, a C1 to C4 group, preferably a methyl group;

X represents an alkyl group having 1 to 16 carbon atoms, preferably from 1 to 12 carbon atoms, more preferentially from 1 to 8 carbon atoms, for example from 2 to 6 carbon atoms or from 2 to 5 carbon atoms. X represents particularly preferably an ethylene, propylene or butylene group, in particular a propylene group.

According to a particularly preferred embodiment, the nitrogenous compound is the reaction product of a polyisobutenyl succinic anhydride and an alcohol or an amine also including a tertiary amine group, in particular a compound of formula (I) or (II) as described above and more preferentially a compound of formula (I).

According to a preferred variant, the polyisobutenyl succinic anhydride reacts with the amine also comprising a tertiary amine group under certain conditions to form a succinimide (closed form). The reaction of the polyisobutenyl succinic anhydride and the amine may also result under certain conditions in a succinamide, i.e. a compound comprising an amide group and a carboxylic acid group (open form).

According to a second variant, an alcohol also comprising a tertiary amine group reacts with polyisobutenyl succinic anhydride to form an ester also comprising a free carboxyl —CO2H group (open form). Thus, in certain embodiments, the nitrogenous compound may be the reaction product of a polyisobutenyl succinic anhydride and an amine or an alcohol that is an ester or an amide and which further comprises a carboxyl —CO2H group that has not reacted (open form).

The quaternary ammonium salt forming the second additive according to the present invention is directly obtained by reaction between the nitrogenous compound described above comprising a tertiary amine function and a quaternarization agent.

According to a particular embodiment, the quaternarization agent is selected from the group consisting of dialkyl sulfates, carboxylic acid esters; alkyl halides, benzyl halides, hydrocarbon carbonates, and hydrocarbon epoxides optionally in a mixture with an acid, alone or in a mixture.

For fuel applications, it is often desirable to reduce the halogen and sulfur content and the proportion of compounds containing phosphorus.

Thus, if a quaternarization agent containing such an element is used, it may be advantageous to implement a subsequent reaction to exchange the counter ion. For example, a quaternary ammonium salt formed by reaction with an alkyl halide may then be reacted with sodium hydroxide and the sodium halide salt eliminated by filtration.

The quaternarization agent may comprise halides such as chloride, iodide or bromide; hydroxides; sulfonates; bisulfites; alkylsulfates such as dimethyl sulfate; sulfones; phosphates; C1-C12 alkylphosphates; C1-C12 dialkylphosphates; borates; C1-C12 alkylborates; nitrites; nitrates; carbonates; bicarbonates; alkanoates; C1-C12 O,O-dialkyldithiophosphates, alone or in a mixture.

According to a particular embodiment, the quaternarization agent may be selected from dialkylsulfate derivatives such as dimethyl sulfate, N-oxides, sulfones such as propane- and butane-sulfone, alkyl, acyl or aralkyl halides such as methyl and ethyl chloride, benzyl bromide, iodide or chloride, and hydrocarbon carbonates (or alkyl carbonates).

If the acyl halide is benzyl chloride, the aromatic nucleus is optionally substituted by one or more alkyl or alkenyl groups.

The hydrocarbon (alkyl) groups of the hydrocarbon carbonates may contain from 1 to 50, from 1 to 20, from 1 to 10 or from 1 to 5 carbon atoms per group. According to one embodiment, the hydrocarbon carbonates contain two hydrocarbon groups, which may be identical or different. By way of example of hydrocarbon carbonates, mention can be made of dimethyl or diethyl carbonate.

According to a preferred embodiment, the quaternarization agent is selected from the hydrocarbon epoxides represented by the following formula (III):

wherein R9, R10, R11 and R12 may be identical or different and represent independently from each other a hydrogen atom or a C1 to C50 hydrocarbon group. By way of non-limitative example, mention can be made of styrene oxide, ethylene oxide, propylene oxide, butylene oxide, stilbene oxide and the C1 to C50 epoxides. Styrene oxide and propylene oxide are particularly preferred.

Such hydrocarbon epoxides may be used as a quaternarization agent in combination with an acid, for example with acetic acid. The hydrocarbon epoxides may also be used alone as a quaternarization agent, in particular without additional acid. Without being bound by this hypothesis, it would appear that the presence of the carboxylic acid function in the molecule favours the formation of the quaternary ammonium salt. In such an embodiment not using any additional acid, a protic solvent is used for preparing the quaternary ammonium. By way of example, protic solvents such as water and alcohols (including polyhydric alcohols) can be used alone or in a mixture. The preferred protic solvents have a dielectric constant greater than 9.

Corresponding quaternary ammonium salts prepared from amides or esters and succinic acid derivatives are described in WO 2010/132259.

According to another embodiment, the quaternarization agent is selected from the compounds of formula (IV):

wherein R13 is an alkyl, alkenyl, aryl and aralkyl group, optionally substituted, and R14 is a C1 to C22 alkyl, aryl or alkylaryl group.

The compound of formula (IV) is a carboxylic acid ester able to react with a tertiary amine to form a quaternary ammonium salt. Compounds of formula (IV) are selected, for example, from the carboxylic acid esters having a pKa of 3.5 or less. The compound of formula (IV) is preferably selected from esters of substituted aromatic carboxylic acid, of alpha-hydroxycarboxylic acid and of polycarboxylic acid.

According to one embodiment, the ester is a substituted aromatic carboxylic acid ester of formula (IV) wherein R13 is a substituted aryl group. R13 is preferably a substituted aryl group having 6 to 10 carbon atoms, preferably a phenyl or naphthyl group, more preferentially a phenyl group. R13 is advantageously substituted by one or more groups selected from carboalkoxy, nitro, cyano, hydroxy, SR15 and NR15R16 radicals. Each of the R15 and R16 groups may be a hydrogen atom or an alkyl, alkenyl, aryl or carboalkoxy group, optionally substituted. Each of the R15 and R16 groups advantageously represents the hydrogen atom or a C1 to C22 alkyl group, optionally substituted, preferably the hydrogen atom or a C1 to C16 alkyl group, more preferentially the hydrogen atom or a C1 to C10 alkyl group, even more preferentially the hydrogen atom or a C1 to C4 alkyl group. R15 is preferably a hydrogen atom and R16 a hydrogen atom or a C1 to C4 group. Advantageously, R15 and R16 are both a hydrogen atom.

According to one embodiment, R13 is an aryl group substituted by one or more groups selected from hydroxyl, carboalkoxy, nitro, cyano and NH2 radicals. R13 may be a polysubstituted aryl group, for example trihydroxyphenyl. Advantageously, R13 is a monosubstituted aryl group, preferably ortho-substituted. R13 is for example substituted by a group selected from the OH, NH2, NO2 or COOMe radicals, preferably OH or NH2. R13 is preferably a hydroxyaryl group, in particular 2-hydroxyphenyl.

According to a particular embodiment, R14 is an alkyl or alkylaryl group. R14 may be a C1 to C16 alkyl group, preferably C1 to C10, advantageously C1 to C8. R14 may be a C1 to C16 alkylaryl group, preferably C1 to C10, advantageously C1 to C8. R14 may for example be selected from the methyl, ethyl, propyl, butyl, pentyl or benzyl groups or isomers thereof. R14 is preferably a benzyl or methyl group, more preferentially methyl.

A particularly preferred compound is methyl salicylate.

According to a particular embodiment, the compound of formula (IV) is an ester of an alpha-hydroxycarboxylic acid complying with the following formula (V):

wherein R17 and R18 are identical or different and are independently selected from the group consisting of the hydrogen atom, the alkyl, alkenyl, aryl or aralkyl groups. Such compounds are for example described in the document EP 1254889.

Examples of compounds of formula (IV) wherein R13COO is the residue of an alpha-hydroxycarboxylic acid comprising the methyl, ethyl, propyl, butyl, pentyl, hexyl, phenyl, benzyl or allyl esters of 2-hydroxyisobutyric acid; the methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, phenyl or allyl esters of 2-hydroxy-2-methylbutyric acid; the methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, phenyl or allyl esters of 2-hydroxy-2-ethylbutyric acid; the methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, phenyl or allyl esters of lactic acid and the methyl, ethyl, propyl, butyl, pentyl, hexyl, allyl, benzyl or phenyl esters of glycolic acid. In the above, the preferred compound is methyl-2-hydroxyisobutyrate.

According to a particular embodiment, the compound of formula (IV) is an ester of a polycarboxylic acid selected from dicarboxylic acids and carboxylic acids having more than two acid functions. The carboxylic functions are preferably all in esterified form. The preferred esters are the C1 to C4 alkyl esters.

The compound of formula (IV) may be selected from oxalic acid diesters, phthalic acid diesters, maleic acid diesters, malonic acid diesters or citric acid diesters. The compound of formula (IV) is preferably dimethyl oxalate.

According to a preferred variant, the compound of formula (IV) is a carboxylic acid ester having a pKa of less than 3.5. For the cases where the compound comprises more than one acid group, reference will be made to the first dissociation constant.

The compound of formula (IV) may be selected from one or more carboxylic acid ester selected from oxalic acid, phthalic acid, salicylic acid, maleic acid, malonic acid, citric acid, nitrobenzoic acid, aminobenzoic acid and 2,4,6-trihydroxybenzoic acid. The preferred compounds of formula (IV) are dimethyl oxalate, methyl 2-nitrobenzoate and methyl salicylate.

According to a particularly preferred embodiment, the quaternary ammonium salt used in the invention is formed by reacting a hydrocarbon epoxide, preferably selected from those of formula (III) hereinabove and more preferentially propylene oxide, with the product of the reaction of a polyisobutenyl succinic anhydride the polyisobutylene (PIB) group of which has a number mean molecular mass (Mn) of between 700 and 1000 and dimethylaminopropylamine.

The composition according to the invention comprises the first additive or additives as described above at a preferential content ranging from 5 to 1000 ppm, preferably from 10 to 500 ppm, and more preferentially from 50 to 200 ppm by weight, with respect to the total weight of the composition.

The Second Additive (Phenolic Antioxidant):

The composition according to the invention comprises a second additive consisting of an antioxidant selected from the compounds comprising a phenol group in their structure.

Suitable antioxidants are selected from di-tert-butyl-2,6 methyl-4 phenol (BHT), tert-butyl hydroquinone (TBHQ), 2,6 and 2,4 di-tert-butyl phenol, 2,4-dimethyl-6-tert-butyl phenol, pyrogallol, tocopherol, 4,4′-methylene bis(2,6-di-tert-butyl phenol) (CAS No. 1 18-82-1), alone or in a mixture.

The particularly preferred antioxidants are selected from alkylphenols such as in particular di-tert-butyl-2,6 methyl-4 phenol (BHT).

The composition according to the invention comprises the second additive or additives as described above at a preferred content ranging from 2 to 500 ppm, preferably from 5 to 250 ppm, and more preferentially from 10 to 150 ppm by weight, with respect to the total weight of the composition.

The Other Additives:

The composition according to the invention may also comprise one or more additional additives, different from the first and second additives as described above.

According to a preferred embodiment, the composition further comprises one or more aminated antioxidants, which may in particular be selected from aliphatic, cycloaliphatic and aromatic amines. Dicyclohexylamine is particularly preferred.

The aminated antioxidant or antioxidants may be present in a proportion ranging from 0.2 to 50 ppm, preferably from 0.5 to 25 ppm, and more preferentially from 1 to 20 ppm by weight, with respect to the total weight of the composition.

According to another preferred embodiment, the composition further comprises one or more metal-passivating agents, selected from triazole derivatives, alone or in a mixture.

“Triazole derivatives” means all the compounds comprising a triazole unit, i.e. an aromatic cyclic unit with five members, including two double bonds and three nitrogen atoms. According to the position of the nitrogen atoms, there are 1,2,3-triazole units (called V-triazoles) and 1,2,4-triazol units (called S-triazoles). By way of example of triazole units, benzotriazole or tolyltriazole can be cited.

The metal-passivating agent or agents are preferably selected from amines substituted by triazole groups, alone or in a mixture. “Triazole group” means any substituent containing a triazole unit as defined above.

The metal-passivating agent or agents are more preferentially selected from N,N-bis(2-ethylhexyl)-[(1,2,4-triazol-1-yl)methyl]amine (CAS 91273-04-0) and N,N′-bis-(2-ethylhexyl)-4-methyl-1H-benzotriazole amine (CAS 80584-90-3), alone or in a mixture.

The passivators described on page 5 of the application US2006/0272597 can also be cited.

The metal-passivating agent or agents may be present in a proportion ranging from 0.2 to 50 ppm, preferably from 0.5 to 25 ppm, and more preferentially from 1 to 15 ppm by weight, with respect to the total weight of the composition.

According to another preferred embodiment, the composition further comprises one or more chelating agents (or metal-sequestrating agents), which can in particular be selected from amines substituted by N,N′-disalicylidene groups, such as N,N′-disalicylidene 1,2-diaminopropane (DMD).

The chelating agent or agents may be present in a proportion ranging from 0.1 to 100 ppm, preferably from 0.2 to 50 ppm, and more preferentially from 0.5 to 20 ppm by weight, even more preferentially from 0.5 to 10 ppm by weight, with respect to the total weight of the composition.

The composition according to the invention may also comprise one or more other additives normally used in fuels, different from the additives described previously.

The composition may typically comprise one or more other additives selected from detergents, anticorrosion agents, dispersants, demulsifiers, tracers, biocides, reodorants, proketane additives, friction modifiers, lubrication additives or oiliness additives, combustion-aid agents (catalytic promoters of soot combustion), anti-wear agents and/or conductivity-modifying agents.

Among these additives, mention can be made in particular of:

a) proketane additives, in particular (but non-limitatively) selected from alkyl nitrates, preferably 2-ethyl hexyl nitrate, aryl peroxides, preferably benzyl peroxide, and alkyl peroxides, preferably tert-butyl peroxide; b) lubrication or anti-wear additives, in particular (but non-limitatively) selected from the group consisting of fatty acids and the ester or amide derivatives thereof, in particular glycerol monooleate, and derivatives of mono- and polycyclic carboxylic acids. Examples of such additives are given in the following documents: EP680506, EP860494, WO98/04656, EP915944, FR2772783, FR2772784 c) demulsifying additives, for example (but non-limitatively) selected from oxyalkylated phenolic alkyl resins (for example the compound CAS 63428-92-2), d) detergents.

According to a preferred embodiment, the composition comprises at least one detergent additive selected from triazole derivatives with the following formula (VI):

wherein

R14 is selected from the group consisting of a hydrogen atom, a C1 to C8 aliphatic hydrocarbon group, preferably C1 to C4, more preferentially C1 to C2, linear or branched, and a carboxyl group (—CO2H). Preferably, R14 is a hydrogen atom;

R16 and R17 are identical or different and represent, independently of each other, a group selected from the group consisting of a hydrogen atom and an aliphatic hydrocarbon group, linear or branched, saturated or unsaturated, cyclic or acyclic, having from 2 to 200 carbon atoms, preferably from 14 and 200 carbon atoms, but more preferentially from 50 to 170 carbon atoms, even more preferentially between 60 and 120 carbon atoms.

It should be noted that we apply the conventional representation rules (bond in broken line and labile bond) to indicate that the position of the hydrogen atom and of the double bond in the triazole ring may change, said formula thus covering both possible positions.

According to a particular embodiment, the triazole derivative has the formula (VI) wherein R16 and R17 are identical or different and represent, independently of each other, a group selected from the group consisting of a hydrogen atom and an aliphatic hydrocarbon group having a number mean molecular mass (Mn) of between 200 and 3000, preferably between 400 and 3000, more preferentially between 400 and 2500, even more preferentially between 400 and 1500 or between 500 and 1500. Said aliphatic hydrocarbon group is preferably a polyisobutylene group (also known as polyisobutene, denoted PIB) having a number mean molecular mass (Mn) of between 200 and 3000, preferably between 5400 and 3000, more preferentially between 400 and 2500, even more preferentially between 400 and 1500 or between 500 and 1500. According to a particularly preferred embodiment, R16 and R17 represent respectively a hydrogen atom and a PIB group as described above or vice versa.

According to a preferred embodiment, the composition of the invention does not contain an antifoaming additive. This is because the good intrinsic properties of the composition according to the invention make it unnecessary to add such an additive. For the record, examples of antifoaming additives are in particular (but non-limitatively) polysiloxanes, oxyalkylated polysiloxanes and fatty acid amides coming from vegetable or animal oils. Examples of such additives are given in EP861882, EP663000, EP736590.

Uses:

The present invention also relates to the use of a composition of additives comprising at least one first additive and at least one second additive as described above, for improving at least one property of a fuel composition comprising at least 85% by weight one or more hydrocarbon fractions having a distillation range lying in the range from 100 to 400° C. and having a paraffin content greater than or equal to 90% by weight.

The improved property or properties are advantageously selected from the following: conductivity, corrosion resistance, oxidation stability, and detergence.

Said first and second additives are as described above. Such a composition of additives may also further comprise one or more additional additives, as described above, and in particular:

one or more aminated antioxidants as described above;

one or more metal-passivating agents, selected from the triazole derivatives as described above;

one or more chelating agents as described above.

A particularly preferred additive composition comprises the following compounds:

a quaternary ammonium salt formed by reacting propylene oxide with the product of the reaction of a polyisobutenyl succinic anhydride the polyisobutylene (PIB) group of which has a number mean molecular mass (Mn) of between 700 and 10000 and dimethylaminopropylamine;

di-tert-butyl-2,6 methyl-4 phenol;

dicyclohexylamine;

N,N-bis(2-ethylhexyl)-[(1,2,4-triazol-1-yl)methyl]amine; and

N,N′-disalicylidene 1,2-diaminopropane.

Finally, the object of the present invention is the use of a composition as described above as a fuel supplying a diesel engine, particularly in a stationary engine or a vehicle equipped with a diesel engine, and more particularly as fuel in a diesel car. The composition according to the invention may in particular be used in the following various vehicles: light vehicles, heavy goods vehicles (lorries with various loads known as “medium duty” and “heavy duty”, household-waste lorries, buses, coaches, etc.) and non-road vehicles (building-site or civil-engineering machinery, tractors, trains, boats).

The following examples are given by way of illustration of the invention and should not be interpreted so as to limit the scope thereof.

Examples

The following examples were implemented using a paraffinic hydrocarbon fraction (hereinafter fraction C1) consisting of a hydrotreated vegetable oil (HVO) the characteristics of which are detailed in table I below:

TABLE I Characteristic Method Value Density at 15° C. ISO 12185 779.9 kg/m³ Viscosity at 40° C. ISO 3104 2.9 mm²/s Cloud point (CP)° ASTM D7346 −36° C. Limit temperature of EN 116 −39° C. filterability (LTF Distillation profile ISO 3405 Initial point 216.0° C. Point at 5% vol. 252.4° C. Point at 10% vol. 262.1° C. Point at 20% vol. 269.8° C. Point at 30% vol. 273.4° C. Point at 40% vol. 275.7° C. Point at 50% vol. 277.8° C. Point at 60% vol. 279.7° C. Point at 70% vol. 282.1° C. Point at 80% vol. 285.0° C. Point at 90% vol. 289.2° C. Point at 95% vol. 293.0° C. Final point 304.3° C. Distilled volume 98.6 ml Residue 1.3 ml Losses 0.1 ml Aromatic compound content EN12916 0% by weight

This hydrocarbon fraction consists of 99.9% by weight paraffins, including 92.6% isoparaffins (hereinafter i-paraffins) and 7.3% by weight n-paraffins.

The exact composition thereof is detailed in table II below:

TABLE II Number of atoms of C n-paraffins i-paraffins naphthenes i-naphthenes 7 2.35 0.39 8 0.09 0.20 0.01 9 0.16 0.43 0.01 10 0.17 0.80 0.01 11 0.14 0.84 12 0.13 0.99 13 0.15 1.02 14 0.86 1.54 0.01 0.01 15 9.55 0.01 0.05 16 2.43 31.15 0.01 17 14.22 18 0.80 30.71 0.02 19 0.23 0.01 20 0.01 0.31 21 0.03 22 0.06 23 0.02 24 0.01 27 0.08 Total 7.29 92.56 0.03 0.12

Fuel compositions were prepared by adding to the above C1 fraction the mixtures of additives detailed in table III below, wherein the proportion of each additive is indicated in ppm by weight with respect to the total weight of the final composition.

TABLE III Additive Mixture 1 (MIX1) Mixture 2 (MIX2) Quaternary 100 137 ammonium salt 1 Composition 2 150 164 Anticorrosion 0 5 additive 3 1 formed by reacting propylene oxide with the product of the reaction of a polyisobutenyl succinic anhydride the polyisobutylene (PIB) group of which has a number mean molecular mass (Mn) of 1000 g/mol and dimethylaminopropylamine. 2 additive composition consisting of di-tert-butyl-2,6 methyl-4 phenol; dicyclohexylamine; N,N-bis(2-ethylhexyl)-[(1,2,4-triazol-1-yl)methyl]amine; and N,N′-disalicylidene 1,2-diaminopropane. 3 tetrapropenyl succinic acid.

The properties of the hydrocarbon fraction C1, before and after each of the above mixtures of additives, were evaluated.

Corrosion Resistance

The method used for evaluating corrosion resistance is that described in ASTM D665A (the standard described in relation to lubricants but applicable to fuels). The principle is as follows: a steel test piece is immersed in a beaker filled to 90% volume with the fuel to be evaluated and to 10% volume with fresh water. The solution is stirred continuously, and the beaker is heated to 60° C. After 24 hours, the test piece is observed in order to evaluate the corrosion present on the surface of the test piece.

The corrosion is notated by attributing a mark in the form of a letter ranging from A to E, A signifying absence of corrosion, and E corresponding to the maximum degree of oxidation.

The results obtained are detailed in table IV below:

TABLE IV Composition C1 C1 + MIX1 C1 + MIX2 Fresh-water E A A corrosion ASTM D665A

These results show that the fraction C1 has very poor resistance to corrosion, and that the compositions in accordance with the invention (C1+MIX1 and C1+MIX2) very significantly improve this property, including in the absence of any anticorrosion additive (C1+MIX1).

Conductivity:

The conductivity tests were implemented in accordance with the method described in ISO 6297. The results obtained are detailed in table V below:

TABLE V Composition C1 C1 + MIX1 C1 + MIX2 Conductivity in pS · m⁻¹ 40 351 459 ISO 6297

These results show that the fraction C1 has a very poor conductivity and that the compositions according to the invention (C1+MEL1 and C1+MEL2) very considerably improve this property.

Oxidation Stability:

The method used for evaluating oxidation stability is the so-called Rancimat method as described in EN 15751.

The test consists of accelerating the process of ageing of the sample by exposing it to heat and to the passage of large quantities of air. It measures the time necessary for oxidation of the product and defines the oxidation stability time. The result obtained is expressed in hours. The longer the time, the more stable the fuel is under oxidation.

The results obtained are detailed in table VI below:

TABLE VI Composition C1 C1 + MIX1 C1 + MIX2 Rancimat 12 h >80 h >80 h EN 15751

These results show that the fraction C1 has very poor stability (it oxidises rapidly) and that the compositions according to the invention (C1+MIX1 and C1+MIX2) very significantly improve this property.

Detergence:

The performances in terms of detergence were evaluated using the XUD9 engine test, consisting of determining the loss of flow rate defined as corresponding to the restriction of the flow of diesel emitted by the injector of a prechamber diesel engine during operation thereof, according to the CEC standardised engine test method F-23-1-01. The objective of this test is to evaluate the suitability of the additive composition tested for reducing the deposits on the injectors of a four-cylinder Peugeot XUD9 A/L engine with diesel prechamber injection.

The tests were implemented with a Peugeot XUD9 A/L four-cylinder engine with diesel prechamber injection equipped with clean injectors, the flow rate of which was determined in advance.

The engine follows the test cycle detailed in table VII below repeated 134 times for a total period of 10 hours and 3 minutes:

TABLE VII Duration Speed Torque Step (s) (rev/min) (Nm) 1 30 1200 ± 30 10 ± 2 2 60 3000 ± 30 50 ± 2 3 60 1300 ± 30 35 ± 2 4 120 1850 ± 30 50 ± 2

The test conditions are as follows:

Flow rate of cooling liquid (step 2 only): 85±5 l/min

Temperatures:

Cooling liquid outlet: 95±2° C.

Oil: 100±5° C.

Air inlet: 32±2° C.

Fuel (at the pump): 31±2° C.

Pressures:

At the inlet of the fuel pump: −50 to +100 mbar

At the outlet of the fuel pump: −100 to +100 mbar

Exhaust discharge pressure (step 2 only): 50±10 mbar

Air inlet: 950±10 mbar.

The following two consecutive phases were implemented, with the same test method for each phase:

-   -   Phase 1 of fouling (or “dirty up”) with a conventional type B7         diesel fuel, conforming to EN 590. The loss of flow rate         evaluated with this first phase is 80%.     -   Phase 2 of cleaning (or “clean up”) with the candidate fuel.

At the end of the test, the flow rate of the injectors is once again evaluated. The loss of flow is measured on the four injectors. The results are expressed as a percentage loss of flow rate for various needle lifts. Usually the fouling values are compared at 0.1 mm of needle lift since they are more discriminating and more precise and repeatable (repeatability <5%). The change in the loss of flow rate before/after test makes it possible to deduce the loss of flow rate as a percentage. Because of the repeatability of the test, a significant detergent effect can be affirmed for a reduction in loss of flow rate, i.e. a gain in flow rate of more than 10 points (>10%).

The results obtained are detailed in table VIII below:

TABLE VIII Composition C1 C1 + MIX2 Loss of flow rate (%) 59 0

The above results show that the composition according to the invention leads to very good detergence results, in terms of cleaning of fouled injectors (“clean-up” effect). 

1. A fuel composition comprising: at least 85% by weight one or more paraffinic hydrocarbon fractions having a distillation range lying in the range from 100° C. to 400° C. and having a paraffin content greater than or equal to 90% by weight; at least one first additive consisting of a quaternary ammonium salt, obtained by reaction with a quaternarization agent of a nitrogenous compound comprising a tertiary amine function, this compound being the product of the reaction of a polyisobutenyl succinic anhydride and of a compound comprising at least one tertiary amine group and at least one group selected from primary amines, secondary amines and alcohols; and at least one second additive consisting of an antioxidant selected from the compounds comprising a phenol group.
 2. The composition according to claim 1, characterised in that the distillation range of said paraffinic hydrocarbon fraction lies in the range from 130 to 350° C.
 3. The composition according to claim 1, characterised in that the paraffin content of said paraffinic hydrocarbon fraction is greater than or equal to 95% by weight with respect to the total weight of said fraction.
 4. The composition according to claim 1, characterised in that said paraffinic hydrocarbon fraction contains at least 50% by weight isoparaffins with respect to the weight of said fraction.
 5. The composition according to claim 1, characterised in that the paraffinic hydrocarbon fraction or fractions are hydrotreated vegetable oils.
 6. The composition according to claim 1, characterised in that it comprises at least 90% by weight the paraffinic hydrocarbon fraction or fractions.
 7. The composition according to claim 1, characterised in that said compound comprising at least one tertiary amine and at least one group selected from primary amines, secondary amines and alcohol is selected from the amines of the following formula (I) or (II):

wherein: R6 and R7 are identical or different and represent, independently of each other, an alkyl group having from 1 to 22 carbon atoms; X is an alkylene group having from 1 to 20 carbon atoms; m is an integer number between 1 and 5; n is an integer number between 0 and 20; and R8 is a hydrogen atom or a C1 to C22 alkyl group; and preferably among the amines of formula (I).
 8. The composition according to claim 1, characterised in that it comprises the first additive or additives in a proportion ranging from 5 to 1000 ppm with respect to the total weight of the composition.
 9. The composition according to claim 1, characterised in that the second additive is selected from alkylphenols.
 10. The composition according to claim 1, characterised in that it comprises the second additive or additives in a proportion ranging from 2 to 500 ppm with respect to the total weight of the composition.
 11. The composition according to claim 1, characterised in that it further comprises one or more aminated antioxidants selected from aliphatic, cycloaliphatic or aromatic amines, and preferably dicyclohexylamine, present in a proportion ranging from 0.2 to 50 ppm with respect to the total weight of the composition.
 12. The composition according to claim 1, characterised in that it further comprises one or more metal-passivating agents selected from amines substituted by triazole groups, alone or in a mixture, present in a proportion ranging from 0.2 to 50 ppm with respect to the total weight of the composition.
 13. The composition according to claim 1, characterised in that it further comprises one or more chelating agents, present in a proportion ranging from 0.1 to 100 ppm with respect to the total weight of the composition.
 14. A use of an additive composition comprising at least one first additive and at least one second additive as defined in claim 1 for improving at least one property selected from conductivity, corrosion resistance, oxidation stability and detergence of a fuel composition, comprising at least 85% by weight one or more hydrocarbon fractions having a distillation range lying in the range from 100 to 400° C. and having a paraffin content greater than or equal to 90% by weight.
 15. The use according to claim 14, characterised in that the additive composition further comprises: one or more aminated antioxidants selected from aliphatic, cycloaliphatic and aromatic amines; one or more metal-passivating agents selected from amines substituted by triazole groups, alone or in a mixture; and one or more chelating agents. 